Currently, radio communication systems such as mobile phone systems and radio local area networks (LANs) are widely used. In the radio communication field, the next-generation communication technology is under discussion to further improve communication rates and communication capacities. For example, the 3rd Generation Partnership Project (3GPP) that is a standards organization has completed or is considering the standardization of the communication standard called Long Term Evolution (LTE) and the standardization of the communication standard called LTE-Advanced (LTE-A).
For LTE-A, the introduction of a heterogeneous network formed by combining radio communication of different types, different standards, and different ranges of coverage is in progress. For example, as illustrated in FIG. 12, a network in which a pico-cell base station 50b is overlaid with a macro-cell base station 50a exists.
The heterogeneous network has a problem with interference between base stations with different transmission power levels. In order to solve the interference between the base stations, a technique called enhanced inter-cell interference coordination (eICIC) is used for release 10 of LTE-A.
This technique is a method of repeating the turning on and off of transmission power of a macro-cell base station and causing a terminal to communicate with the base station and a small-cell base station based on the timing of the turning on and off in order to reduce interference between the macro-cell base station and the small-cell base station.
In addition, Japanese Laid-open Patent Publication No. 2015-29343 discloses a technique in which a certain base station that gives an effect of downlink interference to another base station determines a time division pattern composed of a first time resource and a second time resource limited so that the transmission power of the base stations in the second time resource is lower than those in the first time resource and the certain base station changes the time division pattern based on information on the utilization of resources of the other base station.